Despite the potential importance of weight gain to smoking relapse, there has been virtually no success in eliminating, or even reducing, the weight gain following smoking cessation. Two promising pharmacologic methods for reducing postcessation weight gain are nicotine gum and an over-the-counter drug, phenylpropanolamine gum ([PPA]; Klesges et al., 1990). However, the relative efficacy of these two drugs has never been evaluated and the mechanisms of action of both drugs on weight gain are unknown. Given this introduction, we propose: (1) To determine the efficacy of nicotine gum and phenylpropanolamine (PPA) gum relative to a placebo in the reduction of postcessation weight gain throughout a 13-week combined behavioral and pharmacologic treatment program. Following cessation of the drugs at the end of treatment, we will monitor long-term effects of these drugs on body weight at both a 6- and a 12-month follow-up; (2) To determine the mechanism of action of both nicotine gum and PPA gum (viz., changes in dietary intake, physical activity, or metabolic rate) on change in weight during the course of treatment; (3) To evaluate withdrawal symptoms of smoking cessation as they are moderated by either nicotine gum or PPA gum use during the course of treatment; (4) To determine if PPA and nicotine gum produce an incremental effect on smoking cessation (relative to placebo gum) in a sample of female smokers who are at high risk for postcessation weight gain at posttest and at a 6- and 12-month follow-up.